CompTIA Network +

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CompTIA Network +

Chapter 5

Working with IP Addresses

Objectives


What is the format of an IP version 4 (IPv4) address, and
what are the distinctions between unicast, broadcast and
multicast addresses?


Which options are available for assigning IP addresses
to network devices?


Given a subnet design requirement (for example, a
number of required subnets and a number of required
hosts per subnet), how do you determine the appropriate
subnet mask for a network?


What are the primary characteristics of IPv6?



Working with IP Addresses


When two devices on a network want to communicate, they
need logical addresses.


Most modern networks use Internet Protocol (IP) addressing,
as opposed to other Layer 3 addressing.


Two versions of IP addressed, first we will discuss how IP
concepts are applied to IP
version 4
(IPv4).


Next, various options for assigning IP addresses to end
stations are contrasted.



IPv4 Addressing


Although IPv6 is increasingly being adopted in cor
p
orate
networks, IPv4 is by far the most popular Layer 3 addressing
scheme in today’s networks.



Devices on an Ipv4 network use unique IP addresses to
communicate with one another.



An IPv4 address is a 32
-
bit address. That is typically written
in
dotted
-
decimal notation.

Such as 10.1.2.3


IPv4 Addressing


Notice that the IP address is divided into four separate
numbers, separated by periods.


Each of these four divisions represents
8 bits
, and are called
octets.



IP
addressing


Unique
IP address per host


Unique address per logical network


Communicate
between
LANs without broadcasts


IPv4 Address Structure


IP Addresses (IPv4 only]


32
-
bit value


Example: 11000000101010000000010000000010


Broken into four groups of eight


11000000.10101000.00000100.00000010


Each 8
-
bit value
converted
into a decimal number between
0 and
255, 192.168.4.2



IP
Addresses in Action


IP must do three things

1.
Give each LAN its own identifier

2.
Allow routers connecting LANs to use network identifiers
to send packets to the right network

3.
Give each computer a way to understand when a packet is
intended for a computer on the local LAN or for a
computer on the WAN

IPv4 Address Structure

IPv4 Address Structure


1.
IP must give each LAN its own identifier


Network IDs


All computers on same LAN must have same
network ID


Each computer on same LAN must have a unique
host ID

IPv4 Address Structure



Network information (network ID)


First 8 bits in Class A address


First 16 bits in Class B address


First 24 bits in a Class C address


Host information


Last 24 bits in Class A address


Last 16 bits in Class B address


Last 8 bits in Class C address

IPv4 Address Structure

IPv4 Subnet Masks


Identifies how network subdivided


Indicates where network information
located


Subnet mask bits


1: corresponding IPv4 address bits contain
network information


0: corresponding IPv4 address bits contain
host information

IPv4 Address Structure



Example Class A network address: 114.56.20.33, 255.0.0.0


Network information = 114.


Host information = 56.204.33



Example Class B network address: 147.12.38.81, 255.255.0.0


Network information = 147.12.


Host information =
38.81



Example Class
C
network address:
214.51.42.7, 255.255.255.0


Network information =
214.57.42.


Host information =
7


IPv4
Address Classes

Address Class

Value in First Octet

Classful Mask
(Dotted Decimal)

Classful Mask
(Prefix Notation)

Class A

1
-
126

255.0.0.0

/8

Class B

128
-
191

255.255.0.0

/16

Class C

192
-

223

255.255.255.0

/24

Class D

224


239

N/A

N/A

Class E

240



255

N/A

N/A

IPv4 Address Classes

IPv4 Special Address

Address Class

Address Range

Default Subnet Mask

Class A

10.0.0.0



10.255.255.255

255.0.0.0

Class B

172.16.0.0


172.31.255.255

255.255.0.0

Class B

169.254.0.0


169.254.255.255

255.255.0.0

Class C

192.168.0.0


192.168.255.255

255.255.255.0

Private Address

IPv4 Special Address

Loopback Address

Address Class

Address Range

Default Subnet Mask

Class A

127.0.0.1



127.255.255.255

255.0.0.0

Types of Addresses



Unicast



meaning that traffic travels from a single
source device, to a single destination device.

Types of Addresses



Broadcast



meaning that traffic travels from a single
source device, to all destination device.

Types of Addresses



Multicast



meaning that traffic travels from a single source
device, to multiple, yet specific, destination devices.

Assigning IPv4 Addresses



At this point, you should understand that
network each devices need an unique IP
address
.



However, beyond just and IP address, what
other IP address
-
related information does a host
need to communicate?



And how do does it get them?

Assigning IPv4 Addresses



IP address parameters required by each host to
be able to communicate on the LAN and
beyond.



IP address


Subnet mask


Default gateway


DNS server address



A simple way of configuring a PC, with IP
address parameters is to
statically
configure
that information.


This is
time
consuming, prone to human errors, and is
not practical in large enterprise networks.


Instead of static IP address assignments, many
corporate networks
dynamically

assign IP
address parameters to their devices.


Assigning IPv4 Addresses

Assigning IPv4 Addresses



There are two options when using automatic
assigning of IP addresses.



Bootstrap Protocol (BOOTP)


A method of assigning IP address, subnet mask and default
gateway information to diskless workstation.



Dynamic Host Configuration Protocol (DHCP)



A method of assigning IP address, subnet mask, default
gateway, DNS server, and more.

Assigning IPv4 Addresses



When a device does not have a static IP
address configured and it
can not
contact a
DHCP server, it still might be able to
communicate on an IP network thanks to
Automatic Private IP Addressing (
APIPA).



APIPA allows a network device to self
-
assign an
IP address from the 169.254.0.0/16 network.

Subnetting


Default subnet mask (that is, classful subnet mask) are
not always the most efficient choice.



Fortunately we can add additional bits to a subnet masks
(thereby extending the subnet mask) to create subnets
within a classful network.



To create a subnet address, a network administrator
borrows bits from the original host portion and
designates them as the subnet field
.

Subnet Addresses

Purpose of Subnetting


More efficient use of IP addresses than
classful
default


Enables separation of networks for security


Enables bandwidth control


Subnet mask is cornerstone of subnetting


Extend subnet masks of /8, /16, or /24 subnet by

adding more ones (removing equal number of zeroes
).

Subnetting (how
-
to)


The process


The class rules define the network part


The mask binary 0s define the host part


What’s left over defines the size of the subnet part.


Number of subnets = 2
number
-
of
-
subnet
-
bits



2


Number of hosts per subnet = 2
number
-
of
-
host
-
bits



2


IP addressing conventions define that
two

subnets

per network should
not

be used and that
two hosts

per subnet should
not

be used.


This equates to the formula
2
n
-
2

IP Subnetting Guide

1.
To subnet an IP address we need to setup our work sheet
as follows: (this will aid you in completing the work.)


First, at the top of your work sheet lay out the number line as
shown.




7

6

5

4

3

2

1

0 Power of 2 line


128

64

32

16

8

4

2

1 Answer line







Next, place the subnetting formula at the left of the number line.


Third, write down the base IP address that you will be subnetting,
as shown.


Last, notice the box above the subnetting formula;


this is to place your power of two from the power line.

2
-
2= 192.168.0.0

2.
It is time to start the process of subnetting an IP
address.

a. The first thing that we must do is to decide how many subnets
that you need. This is done by looking at how many ports are
on your router. For example if your router has four ports on
the back and three are going to be used for your network, we
will need to subnet our base IP Address into three networks.


3.

Turn to your work sheet; place the number 3 with a
question mark next to the formula, as shown.

IP Subnetting Guide

2
-
2=3?

IP Subnetting Guide

4. Next, look at the bottom line on the sheet and find the number
that is closest to your answer after subtracting 2 from it.

a.
Then, look at the number above it and place it in the box. (by looking
at the answer line and subtracting 2 from it, we find the 8
-
2=6 and the
number above is 3, so 3 goes in the box) Then strike through your old
answer

5. The next step is to calculate the new subnet mask number.

a.
This is done by looking at the number that is in the box. (From this
number we will be placing a one below the number line starting from
the left, as shown).

b.
Then take the numbers above the ones and add them up
128+64+32=224. Then combine them with the default subnet mask
for that class address as shown.

6.
Now we have to figure out the network separation
number. To do this look at the rightmost one; the
number above it is your separation number.

a.
This number is going to be used to set the beginning address
for each of the three networks. In my example the number is
32. This is the number that we are going to use.


7.

The next step is to create an IP Address for each of our
router ports. This is generally the first usable IP
Address after the network number.


IP Subnetting Guide

8.

Now we need to find the broadcast address. This is
always the last number in the range. To find it,
subtract one from the next network number.


9.
The last thing is to fill in between the router # and the
broadcast #; this is called the VALID HOST RANGE.


10.

Now you are done

IP Subnetting Guide

Classless Inter
-
Domain Routing


Although subnetting is the process of extending a classful
subnet mask (that is, adding 1’s to a classful mask),
Classless Inter
-
Domain Routing
(CIDR)
does both.



CIDR, is used by our ISP’s in the world to control the
addressing groups assigned to them by ARIN.


IPv6 Addressing


With the global proliferation of IP
-
based networks, available
IPv4 address have run out.



Fortunately, IPv6 provides enough IP address for many
generations to come.



IPv6 dramatically increases the number of available IP
address. IPv6 offers approximately 5 * 10
28

IP address for
each person on the plant.


IPv6 Addressing


IPv6 Features:


Simplified header


No broadcast


No fragmentation


Can coexist with IPv4

IPv6 Address Structure

Feature

IPv6

Size of address (bits or
byes per octets)

128 bits, 16 octets

Example address

0000:0000:0000:0000:0000:FFFF:FFFF:0A01:0101

Number of possible
address, ignoring
reserved values

2
128
, or roughly 3.4 * 10
38

IPv6 Unicast

IPv6 Multicast

IPv6 Anycast

IP Address Management

Internet Corporation

for Assigned Names and Numbers

(ICANN)

American Registry for
Internet Numbers

(ARIN)

Internet Assigned
Numbers Authority

(IANA)

ISP’s

(Comcast)

ISP’s

(Verizon)

YOU

North America

Out side North America

Summary


The characteristics of IPv4 were presented, including
IPv4’s address format and a contrast of unicast,
broadcast, multicast data flows.


You examined various approaches for assigning IP
information to network devices. These approaches
included static assignments, dynamic assignment
(BOOTP and DHCP), and APIPA.


Multiple examples and practice exercises were provided
for various subnets calculations
.


The characteristics of IPv6 were highlighted, including
the IPv6 address format and IPv6 data flows (unicast,
multicast and anycast).